New serial log at ~/.octoprint/logs/serial.log

Logs the same content as the terminal tab and is restricted to 2MB in size (hopefully).

Closes #77
Moved configuration description to wiki and removed obsolete information regarding the repository rename.
Merge branch 'devel'
Only log the terminal output to disk if the "--debug" commandline switch is given

 Otherwise slowdowns might be caused on Raspberry Pi when dumping all printer communication to SD